1. Technical Field of Invention
The invention relates to liquid crystal display devices and electronic apparatuses. More particularly, the invention relates to the structure of a transflective liquid crystal display device in which color purity is well balanced both in a transflective mode and a transmissive mode.
2. Description of Related Art
Liquid crystal display devices capable of displaying images using external light, such as sunlight and artificial illumination in bright places and an internal light source, such as a backlight in dark places are provided. That is, the liquid crystal display devices use a display method that includes both a reflective mode and a transmissive mode. It is possible to clearly display images even in dark places and reduce power consumption by adapting the display method including both the reflective mode and the transmissive mode to convert the display mode into the reflective mode or the transmissive mode in accordance with the brightness of surroundings. According to the present specification, such kinds of liquid crystal display devices are referred to as transflective liquid crystal display devices. The number of cases in which coloring is required has recently increased in the field of the transflective liquid crystal display devices due to the development of portable electronic apparatuses and OA apparatuses. In order to meet the requirement, a transflective color liquid crystal display device in which color filters are provided in either the upper substrate or the lower substrate is provided. According to such a kind of liquid crystal display device, in the reflective mode, the external light incident from the upper substrate passes through the color filter, is reflected from a reflection layer, and passes through the color filters again. In the transmissive mode, the illumination light incident on the lower substrate from the backlight passes through the color filters. In a common structure, images are displayed using the same color filters in either of the reflective mode or the transmissive mode.
According to the liquid crystal display device, as mentioned above, it is possible to display colored images by letting the incident light pass through the color filters twice in the reflective mode and once in the transmissive mode. Accordingly, when color filters of light colors are used in consideration of the color during the reflective mode in which light passes through the color filters twice, it is difficult to display those colors clearly in the transmissive mode when light passes through the color filters only once. However, to the contrary, when color filters of deep colors are used in consideration of the color during the transmissive mode in which light passes through the color filters once, since images are darkly displayed in the reflective mode in which light passes through the color filters twice, it is not possible to obtain sufficient visibility. As mentioned above, according to the conventional transflective color liquid crystal display device, it is difficult to display those colors clearly and with high visibility in both the reflective mode and the transmissive mode.
In order to solve the above problems, a liquid crystal display device illustrated in FIG. 11 is suggested (see also, for example, Japanese Unexamined Patent Application Publication No. 2000-111902). The liquid crystal display device is an example of an active matrix liquid crystal display device. In the liquid crystal display device, data lines 101 and scanning lines 102 are arranged to intersect each other. Thin film transistors (hereinafter, abbreviated to as TFT) 103 and pixel electrodes 104 connected to the TFTs 103 are provided around the intersections. The pixel electrodes 104 are made of a metal film such as A1W (an alloy of aluminum and tungsten). The pixel electrodes 104 are constituted of reflection electrodes 105 related to display in the reflective mode and transparent electrodes 106, which are made of a transparent conductive film such as ITO (indium tin oxide), related to display in the transmissive mode. The reflection electrodes 105 are arranged so as to surround the transparent electrodes 106. The centers of the pixel electrodes 104 are transmissive regions T and the peripheries of the pixel electrodes 104 are reflective regions R. Color filters 111A, 111B, and 111C that are narrower than the pixel electrodes 104 are provided in the pixel electrodes 104. Therefore, the transmissive regions T overlap the color filters 111A, 111B, and 111C in plan view. In the reflective regions R, parts of the reflective regions R are colored regions C that overlap the color filters 111A, 111B, and 111C in plan view. The remaining parts of the reflective regions R are non-colored regions H that do not overlap the color filters 111A, 111B, and 111C in plan view.
In this structure, a part of the light incident from the upper substrate in the reflective mode passes through the non-colored regions H. The light obtained by passing through the color filters twice in the reflective mode is obtained by overlapping the non-colored light (white light) that passes through the non-colored regions H with the colored light that passes through the colored regions C. On the other hand, the light from the backlight, which passes through the transmissive regions T, in the transmissive mode passes through the colored regions C. All of the light obtained by passing through the color filters once in the transmissive mode becomes colored light. Therefore, since it is possible to reduce the difference in shading between the light obtained by passing through the color filters twice in the reflective mode and the light obtained by passing through the color filters once in the transmissive mode, it is possible to display colors clearly and with high visibility in both the reflective mode and the transmissive mode by optimizing the coloring layers of the color filters.